Well I'm a high school Biology/Chemistry teacher and here is a couple of ways that I think you can approach this. Don't go in the first day all guns ablaze. Start by asking simple questions, play a little bit ignorant if you will. Ask her what kind of snake it is, what it eats, etc. Gauge her expertise in kingsnakes. Just because they have a degree in Biology doesn't make them an expert on snakes. I've seen plenty of fellow science teachers keeping herps in very bad conditions.

Another approach you can take is with enthusiasm. "Oh cool, you've got a kingsnake! I've got one at home whose enclosure I've upgraded. Do you want its old tank/equipment/etc?" Ask her if you can help with the maintenance of the snake. I've got a couple of kids in each class that I trust in helping me maintain my zoo in the classroom, and I love their enthusiasm and appreciate greatly their help.

Teachers can be pretty arrogant and take helpful criticism in a bad way. Get off on the right foot by taking things slow. The first days of school can be pretty stressful on teachers.

Let us know how it goes!